(1)  Get on like a house on fire = have a very good and friendly relationship.

• My sister and her neighbour Bindu got on like a house on fire.
• I was worried that they wouldn’t like each other but they are getting on like a house on fire.

(2) Have a soft spot for someone or something =  you feel a great deal of affection for them or like them a lot.

• John’s parents always had a soft spot for their eldest son Jose and they took many vital decisions affecting the whole family themselves keeping the other members in the dark in an unfair way.
• I have a soft spot for Thrissur Museum.
• I have always had a soft spot for my cousin Pappachan, now retired from service as an RTO.