Sharing database data

I need to split text data between two users. I'm probably going to use some Android Cloud services (Open to Suggestion), but I'm not sure about a good PC. I didn't want to use DATETIME as a PC, but I don't know any other way. What's a good PC to share between two (or more) users without too much overhead?

If I have in my SharedTable

100 records and my friend only has 2 records in his ShareTable

, then I will need both his (2) PC and my (101) PC to share any changes between the data between myself, he and someone else I am passing this information so it seems like auto-incrementing this is out of the question.

I can't imagine this isn't a common problem, but I can't get my head around myself, so it's hard for me to understand my point of view. If you need more information, let me know.