have a soft spot for or an animal
have a soft spot for (someone or something)
To have a particular fondness of affection for someone or something, often for reasons that hard to understand or articulate. I've always had a soft spot cheesy action films—there's just an earnest goofiness about them that I like. Despite how troublesome he could be, the teacher had a soft spot for Daniel.
have a soft spot (in one's heart) for someone or an animal
Fig. to have a fondness for someone, something, or an animal. I have a soft spot in my heart for Jeff. I'll always be his friend. Elaine has a soft spot for kittens.