ALTERNATE VERSIONS
As Excalibur once found out during the Cross-Time Caper, a journey through numerous alternate realities, none of the team’s counterparts included a version of Rachel, leading to the assumption that she was a person who had very few if any analogues across the multiverse. This was essentially proven correct when Rachel visited the White Hot Room, a nexus to all realities. Whereas her teammate Psylocke saw numerous variations of herself, 
Rachel could only conjure up images of own past selves. This meant that she was unique in some way. [Uncanny X-Men (1st series) #462] Still, other Rachels have been sighted in the multiverse. It is unknown though, if these are true counterparts of Rachel, or just some other daughters of Scott Summers and Jean Grey, who coincidentally have also been named “Rachel.”
In a different version of the “Days of Future Past” scenario, shown in Fantastic Four (1st series) #414, Rachel Summers was not transported back in time, and her lover, Franklin Richards 
survived. Eventually they were married, and had a child named Jonathan Reed Richards. Unfortunately, he was too powerful, went mad and called himself Hyperstorm, threatening the entire multiverse. Blaming his parents and effectively his paternal grandparents for how super-powered beings had been treated in the timeline, Hyperstorm time-traveled to the present with a vengeance in order to make the Fantastic Four pay. He was nearly successful, though in the end Mr. Fantastic lured him into a trap, locking Hyperstorm, empowered by an unlimited power source, into a seemingly endless battle with Galactus, the cosmic devourer with an infinite hunger. As he never reappeared afterwards, Hyperstorm might have died in the conflict.
In another reality, depicted in Exiles (1st series) #12-13, 59, Rachel and Franklin too had off-spring, a redheaded boy they named David. By the time he was six years old, his parents and most other superbeings had been killed by the Sentinels, and David lived in a concentration camp. Eventually, he would have grown up to become a near omnipotent, cruel leader, which is when the dimension-hopping Exiles and their rival team Weapon X came in. Actually, their job was to kill the boy to prevent the millions of human deaths he would cause, but they found a better solution by Sabretooth staying behind and ensuring that David would experience a normal childhood. Unfortunately, Sabretooth failed and, two decades later, he had to kill David nonetheless when he went on a mad rampage.
During another mission to an alternate reality, the Exiles even met one Rachel Summers in person, as was shown in Exiles (1st series) #21-22. Her Earth had been almost entirely 
overcome by techno-organic beings. Rachel (non-Phoenix, but still powerful) was one of the few surviving, non-infected heroes. When Morph noted the absence of Asgardians in that world, he asked Rachel to telepathically contact the Asgardian gods across the dimensional barriers. The gamble worked and indeed the Norse Gods were of great help, for their blood contained a certain regenerative factor from which a serum could be derived to reverse the effects of the techno-organic infection, thus saving humanity on that Earth.
Ten to fifteen years in the future, the re-appearance of Jean Grey heralded the End of the X-Men. 
Though it occurred in deep space, Rachel sensed her mother’s rebirth on Earth. Still, she abandoned her job as manager of Kitty Pryde’s campaign to become Mayor of Chicago only after a series of attacks on the X-Men and their friends. Rejoining the X-Men, Rachel helped her brother Cable beat an infection with nano-robots before traveling to Shi’ar space to face the mastermind behind the recent attacks, Cassandra Nova. Against all odds, Cassandra managed to beat Jean and wrest control over the Phoenix Force from her, and Rachel too found herself overpowered when she tried to claim the Force. Rachel later joined several others in creating the “Tree of Life” from the Quabala and presumably transcended this plane of existence.
In the altered reality of the House of M, Rachel Grey was the bodyguard and traveling companion to Lady Elisabeth Gloriana, alias Psylocke, British royalty after her brother Brian became ruler of all England. Having recently returned from adventuring abroad, Rachel and Betsy became involved in Captain Britain's mission to seal the rift in causality created by the Scarlet Witch's manipulations that created this twisted reality in the first place, to prevent its chaos from spreading to other universes.
In Days of Future Now, a timeline very similar to Rachel’s own developed following several factions of Weapon X participating in the War of the Programs. Director Malcolm Colcord orchestrated the rise of a new Master Mold and Sentinel army, as well as the extermination of most of the active X-Men. However, Brent Jackson of the rival program kidnapped Rachel and intended to use her chrono-skimming ability to undo the timeline in his favor. The War of the Programs ended before Jackson could implement his plan, and Rachel was lost in the shuffle for years, condemned as the Prisoner in Room X for decades. Eventually, the Sentinel oppression of mankind became so bad that Colcord and Jackson united with what remained of the X-Men to carry out that plan.
In the false history of the Age of X reality, Jean Grey manifested her powers and immediately was overwhelmed by a Phoenix event. She died, but so did 600,000 people in and around the city of Albany, New York. As Revenant, Rachel was believed by some to be the ghost of the Phoenix. Mysterious about her past but demonstrably telekinetic, the Revenant lent her power to the Force Warriors maintaining the energy wall around Fortress X every day against the marauding human hordes.
Baron Rachel Grey of Battleworld oversaw the domain of X-Topia. Diverging from the events of Cameron Hodge’s mutant crisis on Genosha, Rachel led the X-Men of X-City. They found themselves at odds with their allies who stayed to reform Genosha after the crisis. An Extinction Plague had developed in Genosha, prompting a quarantine of the island. Havok and the Genoshans were asking for aid from the X-Men’s healer Triage, but Rachel wouldn’t risk him breaking quarantine. Desperate for a solution, the Press Gang attacked X-City and kidnapped
Triage and Rogue, among others. Rachel led the X-Men in a counter-strike on Genosha in response to Havok's daring ploy. This set off a chain of events which uncovered the new Genegineer had deliberately manufactured the plague before reviving Cameron Hodge. Genosha’s leaders Havok, Wolfsbane, Rictor and Tam Anderson died bringing down Hodge, and so Rachel reunited the X-Men of X-City and Genosha to bring them both under her protection.
Also on Battleworld, the domain known as the Sentinel Territories held a version of Rachel’s timeline from the Days of Future Past. Here, the survivors of the mutant concentration camps included Colossus and Shadowcat’s teenage children Cameron and Chrissie Pryde. Rachel and the other surviving X-Men escaped from the camps with a plan to defend the baron, President Kelly, from an attack by rogue Sentinels, as he had been infected with a virus that would make 
them target him. The Pryde children were the last mutants born before the sterilization protocols went into effect. The X-Men believed such a heroic act in the public eye would push Kelly to reform the Mutant Control Act. However, Rachel and Magneto secretly had a different plan. They intended for Chrissie and Cameron to die trying to save Kelly, turning them into martyrs for the cause. Kate Pryde was furious and abandoned her friendship with Rachel when she learned her children would be used as fodder.