If Someone Doesn't Have A Final Will And Testament, Who Has Legal Claim To Their Belongings After Death?

Location: Texas

I'm posting on behalf of my friend, with his permission. My friend is 29M and we'll call him Jack for the sake of privacy. I will be giving him the link to this post so he can read all of the advice, but I will be the one replying to comments if needed.

Jack's dad unfortunately passed away recently. No will has been found yet, and his uncle, who we'll call Richard, has claimed almost everything and is splitting it between himself and his own son, who we'll call Steve. He keeps saying none of the things in the apartment are Jack's since his name isn't on anything, and he's been kind enough to give Jack his dad's truck as well as the belongings in Jack's room, "even though (he) didn't have to." And that without a will, Jack has "no right to give away any of the belongings." Richard and Steve insisted on taking care of everything funeral-related.

For context, Jack was living with his dad in an apartment with only Jack's dad's name on the lease. It was in the same apartment complex Richard lived, but a different apartment.

Within hours of his dad's passing, Richard told Jack he couldn't stay in the apartment since his name's not on the lease. He drove Jack to his mom's, who lives several hours away. Jack wasn't able to take any of his belongings or his three cats. Richard said he would take care of them until he could rehome them. Jack had no say in any of this. He wasn't even given a single night to mourn his dad in peace before being ripped away from his home and pets.

The next day, Richard told Jack he could have his dad's truck if he could get the money to release it from the impound lot. He got the money the same day, but Richard wouldn't go to the impound to get the truck, claiming he was too busy and it wasn't a priority. So Jack's mom drove him to get the truck himself. They went to the apartment and filled the truck with as much of Jack's belongings as they could fit and then drove back to his mom's house.

Since then, Richard has been very low contact with Jack, claiming he's been too busy with funeral arrangements and talking to the VA (Jack's dad was a veteran). Jack has been trying to get in contact about multiple things: how his cat's are doing, where they're being rehomed and if he could get the new owner's contact information to stay in touch, where all of his dad's belongings are going, what the funeral plans are, etc. Jack heard about some funeral plans from a family friend on Facebook, but no one has told him anything directly. Steve told him there haven't been a lot of plans yet, so they probably just "haven't gotten to him yet," but shouldn't the children of the deceased be the first to know? He also told Jack that all of the belongings have been split between Richard and himself.

Jack has two brothers who also have not gotten any of their dad's belongings. Would they be able to take Richard and Steve to court over this since they are the direct descendants of the deceased, or are they basically screwed without a will?