Last, last night, I saw the big beetle in the picture inside our house, so I put it outside. The next morning I saw it again in our house so I put it back in the tree. Last night, to my surprise I saw it again, I decided to put it in my room. While I was brushing my teeth I saw a small beetle, I captured it thinking the big beetle is its mother. I put them together and they were close.
I thought that the big beetle might eat or do something nasty with the other one. I don't know their behavior but that's the rule of nature, eliminate the weak ones. I separated them with half of inch or less in distance.