'Probably a discussion for an alternative thread, but what advice would you offer to someone who had met the love of their life who had children through a previous relationship and didn't want more children?'
I would tell them this person is not 'the love of their life' (it's actually possible for a person to share intense love with more than one person, and people's 'souls' are perfectly complete on their own, they don't need a 'soulmate) because the pair of them have vastly different things they want out of life, so the woman needs to move on if she wants children, because it's never a good idea to compromise what you fundamentally want out of life for another person.
'but women are frequently faced with making the choice between their partner or having children.'
More fool them if they forgo what they want out of life for a man. The world is full of millions of men/partners, but you only get one life.
Personally, I don't believe in 'falling in love', either. It's a conscious decision to keep seeing someone with whom you might share many commonalities or sexual chemistry. It's no accident. For me, that meant no men who had children from previous relationships back when I was single and childfree. No matter how much we got on, I asked right away. If they had any kids I was off because I just didn't want that in my life so it wouldn't have been fair to anyone to continue seeing someone who had them.