Trying to verify information on G G Grandparents

I found my great grandparents, Steen and Thomina Olsen. Then someone on Ancestry.com had info on Steen's parents. He stated his information as coming from IGI. Said it showed Steens parents as Ole Steensen and Helje Gundersdatter with other children being, Gunder, Ingebor, Peder, and Knud. All this seems to fit my family but how do I know his information is correct? He had the marriage date as 23 Jul 1826 and verified that from marriage records, but where did the information on the children come from? Will appreciate any assistance. Shirley [:I]