Context:
When my brother and I have a conversation that refers to our mother , we usually use "my mom" to refer to her. For example: "Have you talked to my mom today?" is a common question we ask.
Now the discussion came up when some of our friends pointed out that it was weird and incorrect for us to say "my mom" since we share the same mom and are siblings and that we should just say "mom". However, my brother and I think it's grammatically correct to use "my mom" since it's technically a factual statement.
I'm trying to find out if our usage is incorrect in English grammar and if our friend is correct that we shouldn't use the pronoun "my" in conversations between siblings.
I just wanted to clarify that while English isn't our native language, my brother and I have noticed that we also don't use the correct possessive pronoun in Spanish. Now what I'm getting from both of the answers posted is that this is more of its technically correct, but it might confuse other speakers as it's not common use.