How do we keep this family tradition..?

So my boyfriend told me a secret he's been holding onto for a little while: he plans to propose in August but didn't tell me exactly when or how he was going to do it. My dad passed away in January of this year & it's a very sternly held tradition in our family that the potential husband has to ask permission to marry his daughter(s). I'm the youngest daughter, my older sister is already married & has been for 2 years. But now that he's passed away who does my boyfriend ask? I don't have any uncles on my dads side (my dads older brother passed away as an infant) & I don't know any of the uncles on my mothers side (they never got along). Even though it's such a strongly held family tradition we never discussed who would take over after Dad passed away. So would it be passed on to my mom? I would really, really like to hold onto this tradition for my fathers sake. Any advice would be wonderful.