Skylight Framing Question and L bracing

New user here - but renovating since 1996. We're in the pre-planning stage for a skylight install. Our roofer will be installing the skylight and I will be building the shaft. While scouting the area we came across "L" bracing right where the bottom of the shaft will start. does any know if the 2x4 section can be removed for the shaft to start? approx 46". An additional 2x4 would be added to the opposite side for the "L". "L" brace runs over our basement stairs and a non structural wall runs parallel 8" behind brace. 2 thoughts are to sister a 2x4 to the existing L brace and remove 46" for the shaft Framing or sister an additional L brace next to existing (then still cut out area for shaft).