Plenty of people still play RSE, but when you need help with the games, please ask in the respective Q&A thread. As for your question, no one can really help you catch them. Here's my advice though:
Always save in front of them, in case something happens. Have a LOT of Ultra Balls, and Timer Balls wouldn't be bad too. Make sure you have some healing items in case your Pokemon get low on health. And make sure you knock the Pokemon you're trying to catch into the red area on the health bar. Also helps if you paralyze it, or put it to sleep. Burning, confusing, Leech Seeding and poisoning them are bad ideas. And also, a problem I had with the Regi trio is that they run out of PP quickly. So maybe don't dwindle them too far into red health, because eventually they'll use Struggle, and that has recoil.
I hope that helps! If you need more help, just ask me or post in the Q&A thread. Good luck with catching them!
Locked.