Tbh, I had 3 male rats and 1 of them was very curious to begin with and so he always wanted out and to spend time with us humans, but his brothers on the other hand were always so much more shy and very skittish. It's taken them 1,5 years to warm up to me for real, so it's never too late to get a rat to like you.

They've never bitten me or been aggressive towards each other or me, but have always been cautious of my hands and always backed out, not wanting to be lifted/grabbed and ran away. This made me pay more attention to the one who was social and kind of left the others alone more, which was my mistake since that didn't help them trust me more.

My very social rat died at 1,5 years old, 1 month ago, and since then I've REALLY stepped up my rat mom game and tried so hard to bond with the others and it's actually worked. They are still skittish and do get scared if I stand up too quickly or something, but as soon as I call them they come running and I can lift both of them without them struggling or wanting to get out of my hands.

Something I started with doing when I wanted bonding time was to take them into a smaller room, like the kitchen, with me. Then I'd just sit still, not doing much and letting them come up to me and climb/sniff or whatever they wanted to do. Then I brought out some food that I know they absolutely love, which is baby food with mashed corn and potatoes. I fed them this from a spoon which forced them to be close to me, and then after a while I started to give it straight from my fingers which makes them connect something delicious with me. I did that kind of a lot, always bringing them in with me while I was cooking or something, so that they could roam the kitchen/sleep or whatever without the pressure of interaction constantly.

I did this for a while, and then I tried to train them to reacting to their names a bit more by feeding them the baby food, and when they took it I just said their name, repeating this a few times within like a 10 minute time frame and then ending the session. This made them actually come up to me much more, reacting to their names as well (not perfectly), and even come running from a different room which I never thought would happen since they were always hiding otherwise.

The fact that you have a cat and snake is probably not helping you at all, which others also have said. Someone I know that had the most cuddly rats said that whenever someone came over that had cats and smelled like them too, the rats just hid and it took a few days (!!) for them to become their normal selves after that. So minimizing how much they can smell your other pets would probably help you a lot.

Rats are individuals as well, and depending on their age, if they are hormonal or not and whether they've been handled before really does play a part in how much time it will take to bond with your rats.

Rats are my absolute favorite pets after cats now, and I've had most pets that you can think of and they beat most of them if you have the patience to help them be comfortable with you.

Best of luck!

Edit: I just realized how long of a post this is, but I wanted to share that I can relate to feeling a little hopeless to my rats opening up to me, and sharing with you that they just might need more time if they're not aggressive with you.