Paying child support for non-biological children?

It is a somewhat complicated question which can not be properly answered solely on the facts you have provided. While it is true that child support continues beyond age 19 if the child is continuing to attend full time education in order to become self sufficient, that does not mean that in all cases, a step parent would be obliged to pay support beyond age 19 nor would a step parent typically pay the full table amount as their table amount payable would be reduced by the amount of child support being paid by the biological parent. Also generally regarding support for children over 19 see the decision of Farden v. Farden from the BC Supreme Court (BCSC) and the decision of the BC Court of Appeal (BCCA) in Darlington v. Darlington to read all of the factors that the court considers in determining the entitlement and quantum of child support payable for children over 19.