How would I write him without that connotation? And if you could explain using si before they love, I get the idea but still don't fully understand. Thank you so much for your help!!

The standard sentence would be "Lo amo ancora". You could also hear "io lo amo ancora" (again, here "io" is a highlighted subject, but it can work because if you say a sentence like that, usually it's in a context where you want to emphasise that you still love someone).

"Si" can be either reflexive (equivalent to "myself", "yourself", etc.) or reciprocal. In this case it's reciprocal because you're talking about two different people. The verb "amarsi" doesn't exist on its own (what I mean by this is that "si" is not usually reflexive with the verb "amare"), so it must have a reciprocal meaning.

You would add "l'un l'altro" when:
1) When you want to emphasise the reciprocal aspect of the verb ("si amano l'un l'altro" is not the standard sentence, but it's not wrong either, it's just emphasised)
2) The verb has a preposition. If you want to say something like "they are talking about each other", you have to say "stanno parlando l'uno dell'altro" ("di", in this case, is the equivalent of "about".
Remember that when you add a preposition, you have to put it in the middle. The first element will always be "l'uno" (or "l'una"), whereas the second element will carry the preposition.

I hope I helped you. There are some things that you can't really guess, but have to figure out as you learn more and more, so don't feel disheartened if you don't immediately understand everything!