Hopefully my story will spread a bit of hope .....
Our DS was also long term single and I'd gotten used to the idea. His sister always said he was just too nice, an old fashioned gentleman.
Anyway, he recently got married, on the same day that he turned 40! In his speech he said something along the lines of, 'If anyone had told me five years ago that I would have moved out of London, bought a house and be getting married I would have said ****, though being a gentleman he didn't actually swear!'
He ended his speech by saying, "My Gran always told my mom that one day I would meet the right person and she was right." How she would have loved to have seen him married and tell me 'I told you so!'
From what I've seen in other cases, better wait for the right person than marry in haste and repent at leisure.
As it turns out they have known each other as friends for many years so there is already a solid basis to their relationship.
Try not to worry about your sons and daughters, we never know who is round the corner waiting for them 