It isn't wrong to be altruistic, it isn't wrong to be part of a group, it isn't wrong to share one's life with another. Humans are social creatures and our very selfhood allows overlap with others. Egoistic isolation and perpetual competition isn't our natural state - we go crazy in solitary confinement.
Funny thing is, Rand would agree with you 100%, here. I'm not aware of her ever claiming, directly or indirectly, that altruism is wrong, group membership is wrong, or that life partners are wrong. I'm not aware of her advocating solitary confinement as a general approach to life.
So it looks like you are knocking down a straw man, rather than any actual arguments proffered.