Letter of Recommedation

Hello everyone,
I am reapplying after receiving a rejection and I’m seeking advice regarding a recommendation letter. Specifically, I am considering asking my former co-founder, who left to start their own fintech startup, to provide a recommendation letter. We worked together for two years during our time at the company. I have already secured a letter of support from my current CEO/co-founder for my mandatory and OC3 requirements. I’m unsure if it would be appropriate to include a recommendation letter from my former co-founder as LOR 3, or if I should seek another reference.