Does [name]Sebastian[/name] work with [name]Kaiden[/name] and [name]Lilia[/name]? I like the name and think they sound ok together but not sure if the style is a little off. [name]Doe[/name] it work?
I think [name]Kaiden[/name] and [name]Lilia[/name] come across as more trendy to me, and in that sense [name]Sebastian[/name] seems out of place as it strikes me as more of a classic. Stylistically, I can’t see it in that sibset, though I think [name]Kaiden[/name], [name]Lilia[/name] and [name]Bastian[/name] would work together.
I think [name]Bastian[/name]/[name]Bastien[/name] is a wonderful suggestion if you’re worried about harmony!
I think [name]Lilia[/name] and [name]Sebastian[/name] are great together! [name]Kaiden[/name] strikes me as very different from both of them, but I still think [name]Kaiden[/name], [name]Lilia[/name], and [name]Sebastian[/name] could work. 
I think [name]Bastian[/name] could work, but I like [name]Sebastian[/name] better, personally. If you love [name]Sebastian[/name], I would go with it, I don’t think names “going” together matters more than truly loving the name.
Good luck!