ANOTHER ADDENDUM BC I CAN'T STOP THINKING ABOUT THEM: it's not canonically confirmed the way ivan's is, but i think till's best dreams are r18 fantasies about ivan.
i've seen this explored in fic sometimes, where till is fantasizing about mizi and it eventually morphs into ivan, and i really really like those kinds of fics bc !!! that is SUCH a good depiction of how i think till's fantasies work.
but ALSO, because ivan is so confusing but also seems to hold all the "power" in their relationship (he's a teacher's pet, he gets privileges nobody else does, he's popular among their classmates, etc), i think a LOT of till's subconscious fantasies would be a reversal of that dynamic of sorts. this is further supported by a patreon-exclusive comic which depicts one of his dreams, actually, and in that one he's the "king" of anakt and ivan is his loyal knight who accidentally (?) kidnaps mizi bc till expressed an interest in her (i am paraphrasing here i also don't remember exactly how it goes sorry).
anyways all that to say is, i think he would be absolutely fucking thrilled to wield that kind of power over ivan. honestly i think if till knew how much effect he had on ivan that would have changed a lot but that's an aside. it's also just like, ivan's so perfectly made up and composed all the time that i think till would want to mess him up and ruin that composure. especially bc ivan only acts that way (bratty and childish) with him. they stopped fighting sometime after getting hit with puberty bc ivan outgrew till and worried about his own strength (so ivan was the one who put a stop to it), but i think till definitely fantasizes about it still. it's a fine line between bloodlust and sexual desire after all.
also, his crush on mizi is a childish idolization of her; she's his muse and goddess, but also someone who's too pure for the messy world they inhabit. so i think this also applies to his fantasies; till wouldn't dare to have many fantasies about her, especially of this nature. it's too "disgusting" to associate with her. but ivan... he's just as messy as till is.
and like till's dragged off for punishment often, a lot of which seems to be solitary confinement, and he's not exactly popular in class either, so i think skinship and physical contact/closeness would be very important for him. he has abandonment issues from his separation from io, but also a loss of physical contact, especially gentler ones. also for all that they never could understand each other in life, both of them always wanted to, and sex and its inherent nature of "revealing" would be appealing to till i think.
AND FINALLY, please just look at scars and remember everything comics. hallucivan shuts up till via kissing him, and shoves his hand up till's shirt, and whispers "weren't you the one who wanted to talk to me?" very provocatively and just behaves very sensually in general. but that's till's imagination of ivan. real ivan didn't do ANYTHING of that sort until he was literally about to DIE. ivan may be a yearner and he may have r18 fantasies but he is also the most passive man ever like he was ready to take that with him to the grave and honestly succeeded at that for the most part.
the top/bottom here is also irrelevant, the important point is that till desires ivan in a much more physical manner than ivan does to till i think. this is also why ivantill are freak4freak. ivan's obsessive, possessive nature of his thoughts are a lot more overtly shown, but till is equally possessive if not more. his just manifest themselves differently, and he himself was also deliberately ignoring them for most of his life (until ivan dies). but subconsciously till always thought of ivan as his, because for all his mixed signals, ivan only acted that way around till.
