We'll ... you're entitled to think anything. But have you considered that even if you say "Father", or "Abba", He is OUR Father by default. Since you are obliged to pray in the Name of Jesus when addressing the Father, you have already mentioned TWO brothers - you and Christ.
Romans 8:29; "For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren"
But probably the best reason to pray to the Father of every Christian as "OUR" is, that our Lord Jesus commanded this.
Matthew 5:1 - 6:9
1 ".... his disciples came unto him:
2 And he opened his mouth, and taught them, saying,
...
Matthew 6
5 "And when thou prayest, ...
6 But thou, when thou prayest, ...
7 But when ye pray, ...
8 ...
9 After this manner therefore pray ye: Our Father which art in heaven, Hallowed be thy name."
Chapter 6:5-9 are still part of the discourse started in 5:1-2 - "HIS DISCIPLES". The words are emphatic.
If you're still not sure, get a Concordance and see how many times it says, "Pray for US".