I wish you well in your search, but a word of caution / advice if I may. Aged 17 my son was in the position of your 'newly discovered' half-sibling and was contacted out of the blue on social media. Whilst he's generally pleased it happened, it has also caused him a lot of emotional pain.
Having felt happy & secure in his world he suddenly found himself experiencing feelings of loss & abandonment by the father he'd never known. Four years later he still suffers feelings of anxiety and insecurity that were never there before, and questions why his 'father' wanted his other children but not him. He is currently on anti-depressants & struggling with feelings of low self-worth, for which he's receiving counselling / therapy.
20 is still very young, and whilst I understand your excitement please remember that real people are involved here - real people with real lives & real emotions - so don't go bursting in like a bulldozer. As well as the feelings it brought out in my son, the sudden re-emergence of my ex brought painful memories to the surface for me too - I was shaking and crying for days afterwards. My husband was devastated too - he'd brought my son up from being a baby and had always been 'dad' - what if my son suddenly stopped loving him?
I had never kept the truth from my son but some mothers do, so remember that too. Perhaps this young man has only ever heard bad things about your father - if your version of him is all 'good' then what will that do to his relationship with his mother, the woman he's presumably lived with all his life? How will you feel if you hear your father being bad-mouthed?
You sound so excited & are clearly are longing to meet him & bring him 'in' to your family - and that's just wonderful - but please, put yourself in his shoes too and don't let your enthusiasm take over your senses.
But to end on a positive note, despite the pain & anxiety my son is happy he met his half-siblings & still keeps in touch. Their different upbringings means they are not particularly close, but when the chips are down they know they are 'family' and can count on each other, and that means a lot to them all, and to me.
