helping your parents to figure it out

> is there a way for me to remote control their computer so I can see
> what they're doing and fix problems myself without having to speak to
> them? if yes: HOW?

Use openssh (disable password authentication, use ssh-keygen, maybe
listen on another port). It allows remote login and X forwarding. You
probably want to see what is shown on local screen, I don't know any
solution for that, maybe x11vnc does this.

For mail problems, administering an MTA used by them and seeing its logs
is very helpful.

VNC allows to take control of a remote desktop... but this desktop should be in the local network because VNC is not secured. SSH is secured but does not let you take control of the a running session (a new session is created).

In all case, you need to know the IP address of the computer you want to connect to. DuckDuckGo (for instance) can easily tell it: https://duckduckgo.com/?q=ip

If the computer is behind a NAT router, you need to configure the router so that:
1) it always attributes the same IP address to this computer;
2) the port you use (by default: 22 for SSH, 5900 for VNC) is redirected to this IP address.

awesome thank you very much. I have a software called Remmina preinstalled in my trisquel 5.0. I expect this to become a nightmare thinking of having to get them to do whatsoever on the router. thanks a lot for your help guys

You can try "Share your Desktop" option in Empathy while using a Jabber/Googletalk account. Perhaps the simplest option.