Bad Grandma

Li
Well the rumors are true...I have a grandson.
I'm a grandmother (not too old yet). As far as I knew I had three granddaughters from my oldest son (two different women). Then I heard that my son my have ANOTHER child...a son out there somewhere. I didn't know what to think. Yesterday for the first time my son sent me a picture of the child. Im a believer of DNA testing, especially in circumstances like how my son gets around but omg that boy looks just-like-my-son! at that age!!!  This little boy is going to be starting kindergarten in the fall. He's FIVE YEARS OLD and I've never laid eyes on him. I feel like SHIT!  Why didn't I follow up on it when I first heard the rumors?  Probably his mother hates our family. I know my silly ass son hasn't done a damn thing for him in any way.  I want to meet him and his Mom. I want him to know us. I want to help take care of him whether it's financially or otherwise just as I've done with my granddaughters. I just feel like a triffeling idiot because how do I approach his mother?  Is she going to be like "where have you been the past five years"?  Or will she be open to the idea?  So far this is the biggest and maybe the only regret I have in life.....not seeking the truth when I first heard about the rumor. 
He's also the cutest little guy I've ever seen, other than my son. Just looking at his pic makes me want to cry. Same smile as my son too. Same hair color. Same cheeks. The only difference is his eyes are lighter than my sons and they seem to change color. I saw a pick of him and they looked blue. Another where they looked green. In one pick they look hazel and brown on another. He is black and Mexican. 
Update:  so I called one of my sons other kids' Mom and she sent me a screen shot of my grandsons mother's FB page and I was able to pull her up and message her. I just told her who I was and that I'd love to get to know her and her son and that I wanted him to meet his sisters and other family. She totally okay with it!!!  I'm so relieved. Y'all just don't know. She actually named him after our family; instead of her own. He even has my father's middle name (it's my sons middle name as well). His initials are the same as my son. So happy right now I'm crying tears of joy. 
His Mom has to be some kinda woman. 
UPDATE: 
Below is a pic of my son. 
Update:  I was talking to my boss, a woman I really respect, and I told her about this situation and she shared with me that the exact same thing happened with her son.  He showed up to her house one day and with a little five year old red headed girl that looked exactly like her younger sister. She also told me that her granddaughter has brought her so much joy that she couldn't get too mad at her son. She says she's 11 and just is the greatest person. It's clear she loves her dearly and is happy she finally got to meet her. 
I think this kind of thing must happen a lot. If any of you ladies have guys who are reluctant to tell their family that they going to have a baby, you may want to at some point, take matters into your own hands. I understand that you don't want to do anything that will hurt you man, most grandmothers want to know their grand kids.
Update:  some had questions about him being Mexican, as he looks fully black. All I can say is, ya never know with babies but his Mom is Mexican. She was kind enough to send me pics from day 1 of his life. He was a preemie and I wasn't even there to pray for him. 
I can't wait to meet this kid.