We study the capitulation of 2-ideal classes of an infinite family of imaginary bicyclic biquadratic number fields consisting of fields k = Q( √ 2pq, i), where i = √ −1 and p ≡ −q ≡ 1 (mod 4) are different primes. For each of the three quadratic extensions K/k inside the absolute genus field k (∗) of k, we determine a fundamental system of units and then compute the capitulation kernel of K/k. The generators of the groups Ams(k/F) and Am(k/F) are also determined from which we deduce that k (∗) is smaller than the relative genus field (k/Q(i))∗ . Then we prove that each strongly ambiguous class of k/Q(i) capitulates already in k (∗) , which gives an example generalizing a theorem of Furuya (1977).