There should be a SkyTeam option through AMS or CDG. KE through ICN might also work.

Note that if you don't have BA status, they charge an additional fee to reserve seats in the business class cabin. It's about $100 per person per TATL segment, so probably about $400 per ticket to India.

JAL or AA/JAL through Tokyo might also do this route, but watch out for transfers between NRT and HND.

For a honeymoon, think about cabin configurations that allow you to sit next to each other in business class and talk. Some 1-2-1 is OK in the center section, but on other aircraft, those seats are angled away from each other. You might prefer 2-2-2, all facing forward, or even 2-3-2 if you can get a window-aisle pair. Some new business class interiors are almost suite but without the guest seat found in many FC suites.

You might want to look at FC fares for comparison. The SQ center double suite would be fabulous for a honeymoon, although sex in the big bed during flight is forbidden.