17-year-old Md Israfil and 15-year-old Robeya Khatun were married about eight months ago
Shamsur Rahman, also a Jamaat-e-Islami leader, was picked up at the capital's Mugda locality on Friday night.
Police claimed he had masterminded and financed many cases of arson, vandalism and explosions during the BNP-led alliance's ongoing transport blockade.
The violent agitation that began on Jan 5 has claimed at least 40 lives.