M304(J)’s DNA parent was M429(JK) and his sibling was M170(I)

“The estimated time to MRCA for the IJ clade is 38,500. The existence of the Haplogroup IJ node has been inferred from the fact that certain mutations are shared in common among all Y-chromosomes belonging to the descendant haplogroups I and J. Until very recently, the lack of examples of Haplogroup IJ* complicated any attempt to deduce the geographical location where Haplogroup IJ first appeared. Both Haplogroup I and Haplogroup J are found among modern populations of the Caucasus, Anatolia, and Southwest Asia tends to support the hypothesis that Haplogroup IJ derived from IJK in the vicinity of West Asia or the Middle East and subsequently spread throughout Western Eurasia.”

I cannot explain why the estimated time frame for the father is less than for the son there.