My sister (30yo) has been going out with a man in his late 50s for around a year. Its serious and it seems like they essentially live together. We have not met him but she wants us to meet him. I find it uncomfortable seeing her with him in photographs as looks the same age as our parents (and isn't far of the same age as them). He has his own children that are the same age as her and has grandchildren. I have been avoiding talking to her about it as much as possible as it makes me uncomfortable. Around a month ago I said over WhatsApp would meet him but am having second thoughts and thinking about telling her I am not sure if I can. AIBU.