I felt exactly like this when my 2 eldest grandchildren were born. I just didn’t feel that ‘DNA pull’.
I felt, and still feel, guilty. I’m surrounded by doting grandparents but really can’t put ‘me’ and ‘doting’ in the same sentence! 🙈 however, over time, I’ve come to care for them and I quite like them now - they’re 7 and 11 now. It’s nothing to do with how much I love my son - their dad - I would die for him.
Then my youngest son had a baby 4 weeks ago and I instantly fell in love with her! So strange 🤔 they live a 10 minute drive from me whereas my older son lives an hour and a half away. Is it do with quality (and quantity) time with said babies?? Plus I’m not particularly called on to babysit regularly or often 🤷♀️ So, no, you’re not alone, so don’t beat yourself up. Just go with it. Babies are quite cute though 😂👍