they really do and i don't know how else you're supposed to interpret charlie's reaction and the things he says other than that... well, he is jealous, and he is getting closer to the admission that his feelings for his & frank's relationship ARE at least a little like that. maybe he doesn't actually want to be frank's partner in a conventional sense but he doesn't see how frank having a partner other than him is going to 'work'. he wants to be exclusive.

there's no room for someone else here. there's no room for frank to have a partner. in the past charlie could conceive of it and even encouraged frank to find love, but he can't anymore.

personally i would love to just read this as "if frank wanted love, why didn't he consider me" BUT charlie doesn't really get what frank wants out of this golden bachelor situation (dennis: fame? attention? to bang a bunch of old ladies?), but he thinks he may have been able to help, they could change things in their relationship, or at least he wanted frank to discuss it with him first.