BIOGRAPHY - Page 2
Soon after, Colossus and the X-Men met a young girl named Kitty Pryde, who would later join the team as Sprite. Piotr and Kitty became close, though at the time both were too shy to fully admit their feelings for each other.
When Arcade was held hostage by Dr. Doom, his associate Miss Locke captured the X-Men's loved ones in order to force them into rescuing her boss. Colossus' sister Illyana was among the ones taken. Though the X-Men did as told and encountered Dr. Doom, secretly a few reserve members entered Murderworld, 
trying to free the hostages. Both groups were successful. Happily reunited with her older brother, Illyana was allowed to stay with Piotr in the States. Xavier telepathically taught his X-Men Russian, so that they could commune with the girl and Kitty would often read her bedtime stories. [Uncanny X-Men (1st series) #145-146, 148, 153]
While Colossus and the others were exploring Magneto's alien city in the Bermuda Triangle, which the X-Men had taken over as temporary headquarters, Illyana was lured away by the demon Belasco. The girl wandered off and fell through a stepping disk into the other dimensional realm of Limbo. Colossus and the X-Men traveled into Limbo after her and battled Belasco over the child’s 
fate. They succeeded in rescuing Illyana - but the girl they brought back was seven years older. Thanks to Limbo's unique temporal qualities, Illyana was now a teenager, having lived half her life in the demonic realm. Piotr offered his fullest support to his sister, who was very secretive about her experiences in the nether realm, though at the same time he wondered how he could ever explain their parents what happened to Illyana. [Uncanny X-Men (1st series) #160]
During a mission in space, the X-Men were injected with Brood embryos which were slowly metamorphosing them into "sleazoids" from the inside. The certainty that they was going to die a horrible death caused the relationship of Piotr and Kitty to grow more intense. Despairing, Kitty asked Piotr to make love to her for the first, and probably last, time. Piotr declined, telling Kitty he cared too much for her to go through something so special under such awful conditions. Instead, they held each other that night and, the next day, successfully fought the Brood Queen on the alien’s homeworld. In the end, they were freed from the embryos by the Acanti, a race of space whales that had been oppressed by the Brood for eons. [Uncanny X-Men (1st series) #161-166]
Back on Earth, the couple grew even closer and officially started dating. During such an occasion, the couple was attacked by Brotherhood members, Pyro and Avalanche. At first, the pyrokinetic mutant heated up Colossus to the point where he would nearly melt and Avalanche shattered five 
tanks filled with liquid, absolute near-zero cold nitrogen on top of him. The temperature shock caused the metal to crack and blister and the agony of Piotr was all too visible from the expression on his frozen body. It took the combined powers of Rogue and the Morlock Healer to save the life of Colossus, though in exchange Kitty had to fulfill her promise to stay with Caliban by marrying him. If he had not later released her from that vow, she would have been forced to live underground among the Morlocks. [Uncanny X-Men (1st series) #174, 177-179]
Despite this testimony of her love, Colossus began to question her feelings when she spent more and more time with fellow computer genius Douglas Ramsey, as he had no access to that part of her life. However, it was actually Piotr himself who was responsible for the relationship 
not lasting. When the Beyonder summoned Earth's heroes to his Battleworld to fight the Secret Wars, Colossus and the other X-Men were taken while Kitty was left behind. While on Battleworld, Colossus met a beautiful healer named Zsaji and fell deeply in love for her. Though she at first was with the Human Torch, Zsaji soon realized that Colossus was much more serious in his affection. Piotr was heartbroken when she died, exhausting her healing powers to save the fallen heroes who had been defeated by the villains. [Uncanny X-Men (1st series) #180, Secret Wars (1st series) #5-12]
After the heroes had found a way home, Colossus, in his grief, confessed all to Kitty, promptly ending their relationship. Wolverine hypothesized that what Colossus felt for Zsaji wasn’t love but that he was scared of making a commitment to Kitty and this was an easy way out. However, the damage was done, and Kitty left the team for a time to sort things out. [Uncanny X-Men (1st series) #183]
At a time when several members of the team were absent, the X-Men found themselves against the Dire Wraiths, an alien race with magical abilities. Hopelessly outnumbered, Professor Xavier sent Illyana, who in the meantime had joined the New Mutants, to aid them. Up until now, she had kept her skills as both mutant and sorceress secret from her brother, fearing his reaction, but hiding was no longer possible. Once the villains were defeated, Illyana confessed to Piotr what she had experienced in Limbo and, naturally, he comforted her and promised to be there for her. [Uncanny X-Men (1st series) #189]
Shortly afterwards, Kitty returned from her leave of absence and she and Colossus patched up their differences and became uncomfortable friends. [Uncanny X-Men (1st series) #197]