They do complement one another, but it is far from an equal relationship. While portraying the two humans as created in the image of God, Milton is careful to stipulate that they are "Not equal, as their sex not equal seem'd." Adam is made for one purpose, Eve for another:
For contemplation hee and valour formd/For softness shee and sweet attractive Grace/Hee for God only, shee for God in him: [her looks implied] Subjection, but requir'd with gentle sway/And by her yielded, by him best receivd/ Yielded with coy submission, modest pride/ And sweet reluctant amorous delay.
Adam receives the gifts of reason and free will, and he is accountable only to God. Eve, on the other hand, must submit to Adam, to whom God has delegated absolute authority. In fact, we see later in the poem that the Fall occurs because Adam and Eve both fail to live up to their God-given roles: Eve does not obey God's commandment; Adam does not enforce it.