The driver and a passenger in the truck were uninjured.
Irish police believe Lily and the elder Doug may have originally been from Ireland.
The collision happened at Begern, around two to three miles from Ballinaboule, at around 6.30pm. Hard shoulders on either side are delineated by broken yellow lines and in the middle of the road, for a considerable distance, a central reservation area, approximately two metres wide, had been painted and drivers are not permitted, for safety reasons, to enter it.
They had rented a vehicle at Shannon Airport and were driving to New Ross for the wake of Winnie Keevey, a sister of the woman killed in the crash.
Gardai have launched an investigation and are appealing to anyone who witnessed the incident to contact them immediately. On Tuesday afternoon, his partner Susan Schulze paid tribute to him in a Facebook post.
A statement by the force added: "Steve was a proud father who left behind two daughters, age 11 and 10, who were his pride and joy".
"He showed me true love. I love you Steve and I will love you forever and a day".
Bosses with the Bolingbrook Police Department hailed the dad-of-two - badge #1126.