The answer is not entirely clear, but it mostly started when Firestar saved her in the battle with RiverClan, before she fell off the gorge in the second book in the original Warriors series, Fire and Ice. She began to realize that he wasn't such a bad cat after all and started paying more attention to him rather than torturing him with Dustpaw. She soon started to fall in love with him when she realized that they had similar personalities, similar ages, and that he was a very handsome tom.
Sandstorm realized she loved Firestar during their time together in the forest, as they faced challenges and worked together to protect their Clan. Their bond grew stronger over time, culminating in a deep love and respect for each other.
Firestar
He also loved spottedleaf, but his mate is sandstorm. Cinderpelt loved him but he never knew.
Yes, Firestar is in love with Sandstorm.
That Firestar has stopped loving Spottedleaf in the same way as Sandstorm and he is ready to move on from her.
The warrior cats technically don't "marry" each other. They become mates. But firestar is mates with Sandstorm although he loved Spottedleaf before her. Cinderpelt also liked Firestar.
Well....because she fell in love with him, I guess. But it was a little rocked by Spottedleaf, who died, but Firestar/heart still loved her. But he found out later Spottedleaf didn't mind him loving Sandstorm, and they became mates. I don't know exactly why Sandstorm started loving Firestar, but they love each other very much through the series.
Firestar began to develop feelings for Sandstorm during the course of their adventures together in the original "Warriors" series. Their relationship deepened as they faced various challenges and shared important moments, eventually culminating in them becoming mates.
Scourge had feelings for Sandstorm, but it was more of a one-sided crush from Scourge's perspective. Sandstorm's heart belonged to Firestar.
Sandstorm's first apprentice was Sorreltail.
Yes they are mates. In the darkest hour FIrestar admits to himself that he loves Sandstorm. And she loves him as well! They have two kits in FIrestar's quest named leafkit and squirrelkit and leaf paw, who become leafpool and squirrelflight!
Yes, Firestar has two daughters with Sandstorm, Leafpool and Squirrelflight.
Many cats in the Warriors series, particularly those from ThunderClan, respect and love Firestar for his leadership and wisdom. Firestar has formed strong bonds with his Clanmates throughout his time as leader, making him a beloved and respected figure among many cats in the series.