Maternity Leave

First of all congratulations on your baby!
I’m unsure about Ontario as I live in BC, however, EI in BC is differentiated between Materinity benefits (15 weeks for the person giving birth) and parental benefits (any parent, or adoption parents). I do believe that it should be the same across provinces though.

The 15 weeks is most likely for the maternity benefits which carry over to parental benefits (~40weeks). This is assuming you are applying for the regular Mat leave. The other option is the extended mat leave of 1.5 years which you get paid a little less each payment but it extends over to 1.5 years instead.

Check to see if you get parental benefits and ive heard from service Canada that you can take parental EI simultaneously with you Mat EI.