If you are friends on facebook and he posted a status about it, then send a message sure , if you are not in contact and there's no way he would expect you to find out like you're not close to his family or his best friend or anything, then don't text. Like if you found out through a friend of a friend or something, then it's a little stalkerish for you to text him. Like I'd personally find it weird if my ex from a while ago randomly found out about my uncle's death last year and sent me a text about it to be honest. It just looks like you're using a death as a way to contact him if there's no close way of you knowing and that's not cool. Again, if he publically said it on some social media where you are his friend, then by all means, or if you are close to his mother, sister , best friend or good friend, then by all means because that makes sense but if you found out through a far connection, then don't, it just looks like you just want to contact him for yourself. If he texts you to tell you, then of course reply If you are going to contact him, just say hi, how have you been I've been thinking of you lately and then he could tell you about his grandfathers death and you could reply with your condolences and that looks much more natural

Well, I have his sister on facebook and I have his cousin on instagram which they posted about it. Then my friend has him on facebook and he posted about being really depressed and how this pain will never heal, so I really don't know what to say. But his family that I have on social media posted about it.