Ah! Adorable twins Marlien and Coliena Reentmeester are on Madewell.com in a Sisters in Style feature. I've kept track of their style for the last couple of years, as seen in these posts about The Lucky Shopping Manual and Lonny Magazine.
Thanks to Marlien, I might have to give the Madewell Widelegger jeans in Amarillo Wash another glance. Though if the temps this weekend are any indication of what is to come—going over 90 degrees–I will only want to wear the tiniest of breathable fabrics for the next couple of months.