I don't have any friends who live near me. I don't have a partner or children either. I'm a right saddo. 
No seriously, I have lots of acquaintances through work and hobbies. I, on the odd occasion (i.e. a couple of times a year) go out with them for example to a Christmas party but I don't interact with them socially otherwise. I get on well with them and we chat but because I'm very reserved it's hard to cross over the boundaries into proper friendship. I feel a bit of an outsider as well as so many of them are in relationships and/or have children so I have nothing to talk about in those areas, which are often the main topics of conversation. Really, I'd love to find a group of single women but don't know where I'd find them.
My closest friend was my ex partner and we're not really on speaking terms anymore. I used to hang out with his group of friends and I really liked them but obviously when we split up I lost them all as they were his friends really, not mine. I have two other friends who live a distance away who I communicate fairly often with online. They're the people I turn to for emotional support.
I do feel sad sometimes. Like I had a relative ask me recently if I was spending my birthday with friends and I didn't know what to say....I could hardly say no because I don't have any. I hate birthdays now because they just remind me how socially isolated I am. Otherwise I'm okay with it. I enjoy my own company, I enjoy travelling and going shopping on my own. I think I feel happy with it, if happy is the right word because I'm only 28 and in reasonably good health so am able to be independent and go off and do what I like. Whether I'll feel the same in 50 years when I've got arthritis and struggle to get out of the house, probably not so much.
Having said that, my widowed grandmother goes on holiday with friends lots and is always out and about seeing people yet still always complains about how lonely she is, especially in the evenings. I don't think any number of friends can make up for her husband not being around. If your FIL is used to his own company, he might cope better than you think.