If I'm honest I do not know how to love another adult (with exception of maybe parents) unconditionally.
If I'm really honest I do not know how to love unconditionally period. I can't associate unconditional love with my xah or any other romantic interest or even friend. My love is all about conditions and trying to get needs met like was described up thread in the Fable of Two Co-Dependents. I grew up being told I was loved. I grew up being shown love and affection without neglect or abuse. I grew up very mistrustful of love none the less. I was afraid then and I'm afraid now. I don't know how that happens for sure but I do know that I love my children unconditionally (nothing they do could result in me not loving them) - but I don't think I have been emotionally healthy enough, nor did I ensure a healthy environment, for them to really feel that unconditional love. That sense of worth, perfectness, and security in the center of their beings. They would tell you I love them (if they could articulate such a thing) but I do not think they 'feel' that security of unconditional love. They ask me to often if I love them. It isn't how I treat them because I love them and tell them so and am tender and attentive - but it is about my own internal health (or lack of it) that keeps them off center. We can't trick kids. If we are insecure in our internal selves - they will be too. This is what propels me to further and further my own recovery and this thread is something really great and useful to me.
ETA: I deleted some further rambling because it barely made sense even to me, lol. This thread gives me lots to ponder.