Here, Gloucester reveals that, in addition to his illegitimate son, Edmund, he also has another son "by order of law." ("By order of law" just means Gloucester's other son is legally recognized as a legitimate heir. In other words, this other son isn't a "bastard" like Edmund. Or Jon Snow.)
What's interesting about this passage is that Gloucester says he doesn't favor his legitimate son over Edmund. Gloucester's legitimate son, he says, "is no dearer in [his] account." We can't help but notice that the play is full of speculation about which children are most beloved by their fathers. Recall from a previous passage (1.1.1-6), Kent and Gloucester wondered which son-in-law King Lear liked best. And we know that Lear favors Cordelia over Goneril and Regan.
We should also point out that the more general question of "who loves who the most" turn up again when King Lear stages a love test, demanding to know which daughter can say she loves her father more than everyone else. Seems like Shakespeare is raising the following question: Is love (especially family love) quantifiable? :lock: