I have two adult DCs, one is 36 in December, the other 34 in April.
Neither are married and neither have ever been in a relationship although the elder did have an on/off thing with a girl last year (more 'off' than 'on'.)
I just feel sad for then both and I know both would like to settle down and have their own families. But they don't seem able to meet people. I'm widowed so I do feel awful really that I have so few links to blood family.
I'd never dream of voicing it to them as they might not have wanted children - it's the fact they do and have not had the opportunity that breaks my heart for them.