
There are some help projects on Geni.
You can find some links on this project: https://www.geni.com/projects/Nederlandse-handleiding-GENI-voor-Dummies/13048 (English version, bottom of page)
Go to that profile. Follow illustrated directions here https://help.geni.com/hc/en-us/articles/4408886222999-How-do-I-use-...
to merge him with your version of your father.