It's very common. I was a wreck when my dad died. I was an absolute wreck when my childhood cat died when I was in college. To the point it became a family joke a decade later not to bring up the cat's name around me because I would burst into tears.
My dad was this way with his last cat. I feel bad I kind of brushed it off. He was retired and very close to that cat. He said he would never get another cat because he was in his 70s and it would outlive him. My dad died from cancer a few years later---and when he was becoming incoherent--he mentioned the cat

. We joked he loved that cat more than the rest of us. I am convinced the cancer came back from the stress of losing that cat. Hopefully- they are reunited in heaven