GRONI is the only repository for birth, death and marriage records in what is now Northern Ireland, from 1.1.1922 onwards. (Ancestry and other websites don’t have them).
Births in Northern Ireland within the past 100 years, marriages within the past 75 and deaths within the past 50 aren’t searchable on-line. They are open to the public, just not on-line. If you know all the key details eg exact date and place of birth, parents names etc, you can order a copy of a certificate from GRONI for £15.
https://geni.nidirect.gov.ukBut if you don’t have all the information GRONI need, you need to get in touch with them to get a search done. Contact details for ringing or e-mailing GRONI:
https://www.nidirect.gov.uk/contacts/contacts-az/general-register-office-northern-irelandAlternatively if you live near Belfast, you can go in person to either GRONI or PRONI (both in Belfast). They are the only places where you can search recent records, right up to those registered yesterday. You can view each cert there for £2.50, and if you want a certified copy it’s an extra £8. (Posted out in 2 to 3 weeks time).