Both manga feature a couple who used to be enemies at some point, but who ended up traveling together and growing feelings for each other. Both of those series are action adventure ones, so it's highly possible that you'll like one if you liked the other one.
In both manga there was this big battle between and an end boss and a hero (or heroes in case of Lost Seven). Years later, one of the two meets up a descendant of the other, they start traveling together and grow feelings for each other. It's just that, in case of Legend of Maian we have the descendant of the hero traveling with the end boss and in Lost Seven we have the descendant of the end boss traveling with the hero. If you liked one of those two series, the other one might be worth a shot.
Köinzell is a master swordsman who, along with thirteen other heroes, was sent by the Szaalenden Empire to block an invasion of their enemy Wischtech. Along the way three died, four betrayed the others and seven defeated the traitors and returned as heroes. At least, that's what people believe. In reality the ‘Seven Heroes' were the real traitors, defeating the four true champions after the seven had fled the battle in cowardice. Köinzell has bided his time for twenty years, honing his skills and recovering from the brink of death so that he may avenge his fallen comrades. The time for vengeance has finally come and all who stand in his way shall be dismembered without hesitation, but it won't be easy as everyone believes the lies of the traitors. With all the soldiers in the land and the public against them, Köinzell and his ragtag allies may have to sacrifice everything if they are to prevail against the might of the entire nation.
This is mostly a gut feel recommendation. Sure both manga are action adventure series and in both there is a plot revolving around 7 heroes, but just that in case of those two series would not be enough. Nonetheless something tells me that fans of one of those manga could like the other one as well.
P.S. A word of warning: Ubel Blatt has some mature themes going on. At leas they get greatly reduced after the first few volumes.