Your lovely friend is only lovely in you eyes. I think he's a total prick.
Even you are saying "I felt he was leading her on a bit and told him so." What form did his 'leading her on' take? According to you, he told her he wasn't interested in sex, never wanted children - and since she is "now pushing for marriage" presumably told her he didn't want to get married. So again - what form did his 'leading her on' take? Because leading someone on involves promises you have no intention of keeping - so what promise did he lead her on with?
And if he didn't want children, he should have used contraception, be that condoms or a vasectomy. She didn't get pregnant on her own, did she?
Is he normally this gullible? A woman who "told him at the beginning that she wanted children more than anything in the world" then "changed her mind and didn't want a baby after all". Aye, right. And he believed her that withdrawal "was 99% effective". Aye, right again. And he "doesn't even understand how this happened." Aye, triple right!
Actually, scrub that; he wasn't gullible - he is LYING. He knew she still wanted children. He knew he wasn't taking any contraceptive precautions and he must have know she wouldn't. But he's a lazy self-absorbed arse who didn't really think about consequences, because it suited him to ignore them.
And look at you - calling her a gold-digger with your "He is wealthy and comes from a loving and close family . She is the opposite." And your "I really don't trust her at all." Have a word with yourself!
Your friend is an arse. And you aren't exactly smelling of roses either.