As per my posting yesterday, Kennedy's correspondence to the Pope and the reply here's a great op ed in the NY Times on their dichotomy over the big issue
What separated them was abortion.
Along with her husband, Sargent Shriver, Eunice belonged to America’s dwindling population of outspoken pro-life liberals. Like her church, she saw a continuity, rather than a contradiction, between championing the poor, the marginalized and the oppressed and protecting unborn human life.
Her brother took a different path. Not at first: In 1971, in a letter to a voter that abortion opponents would have many opportunities to quote, he declared that “wanted or unwanted, I believe that human life, even at its earliest stages, has certain rights which must be recognized — the right to be born, the right to love, the right to grow old.” But like many other Catholic liberals, from Joseph Biden to Dennis Kucinich, he moved leftward with his party, becoming a down-the-line supporter of abortion rights, with a voting record that brooked no compromise on the issue.
For abortion opponents, cruel ironies abounded in this sibling disagreement. Because of Eunice Shriver’s work with the developmentally disabled, a group of Americans who had once been marginalized and hidden away — or lobotomized, like her sister Rosemary — was ushered closer to full participation in ordinary human life. But because of laws that her brother unstintingly supported, that same group was ushered out again: the abortion rate for fetuses diagnosed with Down syndrome, for instance, is estimated to be as high as 90 percent.
In 1992, Eunice participated in the last significant effort to push the Democratic Party away from abortion on demand, petitioning her party’s convention to consider “a new understanding” of the issue, “one that does not pit mother against child,” but instead seeks “policies that responsibly protect and advance the interest of mothers and their children, both before and after birth.” ...