LW #1: Rowan had no legal obligation to take custody of her sister. You seem to think she had a moral obligation to do so, but it's also reasonable for a 21-year-old to look at her life and say "nope, I'm not ready to take responsibility for a child." Rowan may have been self-supporting, but that doesn't mean she was financially able to support a child, even an older one that needs less childcare. Besides, if someone says they'd rather enjoy their 20s than have responsibility for a kid they didn't produce, do we really *want* to make them take that responsibility?

That said, there's a lot of space between "I am the legal guardian of this child with all the responsibilities pertaining" and "I have nothing whatsoever to do with this child". Did Rowan blow off her sister as soon as sister went into foster care, or did she make an effort to stay in contact? Did she reassess her situation every couple of years and actively decide that she still couldn't provide Rue a home, or was Rue never a factor in her plans?

And that said -- LW1, unless Rowan is utterly fabulous in every other way that matters to you, I'd skip the couples counselling and break up. If you'd been together for a couple years, counselling would make sense, but you haven't even been dating for six months yet. (But if you do want to keep up the sexytimes and you're a penis-haver, condoms condoms condoms. Don't risk creating a child with someone you don't trust to be a co-parent.)