Hi Julie, I'll try to answer your question about social custom here.
Indonesia is an eastern country. Sex is not allowed to a couple who hasn't married. They will be judged as bad person in their environment and actually there is a punishment if they are known doing like that before marry. Unfortunately the law is not work properly and the fact that social behavior in Indonesia has already mixed by many countries. So sex is not a taboo thing anymore. but it still impolite thing to be talked.
About relatives, I think it same with other country. We always gather in our celebration day. For example I as the moslem, I always gather with my whole family in Idul Fitri. We visit our other relatives to make good communication with them. It also happen with Christian in their Christmas. Hindu and Budha too...
Relatives, neighbor and friend are really important here. In some events. In my place, there are some event about wedding, thanksgiving (but different with US, we do it in many things such as the baby born, send a prayer to our relatives who had passed away, new house, etc). In that time, the role of relative and neighbor are really important. They help to prepare food, to send invitation, To manage the event, etc. We are very close to our family.
We respect and take care for old people. As the children, we have an obligation to take care our parents when they are old. So they wouldn't go to nursing home because we are here for them. And the fact that they've already take care for us when we are child, so we must return their favor.
As the children too. Mostly we are obedient to our parents and or someone who are older such as grandparents, uncle, aunt. Mostly we must follow what they ask (what I mean here is good thing). And we never call them with their name but we must call their status. Grandma, uncle, aunt, etc. And it happens too when we call our older or younger siblings. We don't call their name but "Kakak, mas, mbak" for older siblings.
That happen in my environment but I think every place here has different social custom :)