Well. I think it depends on how strong your concern and commitment to you and yours family’s privacy is. In my case is kind of the same story, the people doesn’t really care about privacy and WhatsApp is the mainly used messaging app. But I convinced them, here’s how:

The first thing that’s important to notice is that you had the same mentality as your relatives in some point, but that changed and there was a reason for it. If you find the way to communicate them that reason and you make them feel what you felt when you started to care about your privacy then there are good chances that they not only install Signal to talk to each other but also to actively care about their privacy. This approach could even potentially spread the behavior, that is, they seek to make their close ones with the importance of privacy.

There might be some issues, specially with the oldest members of your family, because sometimes for them is difficult to adapt to a new tech tool and they might not even be willig to try. However, if you first convince the other members and they support you, it may become easier to get it with the oldest ones.

For me there’s no price for the privacy in the age we live, so I would not give up and do not so in the task of raising awareness in my acquaintances about the importance of protecting this invaluable treasure. (That’s also why I’m posting this :D).

So, if you decide that you want to try it, I wish the best of the lucks for you.

Be the change you wanna see in the world. Start by ditching WhatsApp yourself, or at least aggressively reducing your usage of it in favor of Signal. Let your friends and family know that you’re only reachable on Signal now and see what happens. You don’t have to ask them to switch; just to use Signal if they wanna contact you.