Jessica Simpson and Ashlee Simpson Ross enjoy ski vacation with husbands

Jessica Simpson and her sister Ashlee Simpson Ross are enjoying a couple's vacation with their respective husbands.

The singers hit the ski slopes and Jessica, 39, documented the family bonding session with an Instagram post on Monday night. Jessica posed alongside her husband, Eric Johnson; sis Ashlee, 35, and her husband, Evan Ross, on top of a snowy mountain in Aspen, Colorado.

“Lucy in the Sky with Diamonds,” Jessica captioned the shot, quoting the famed Beatles song, adding the has tag "#ASPENEXTREME."

The day before, Jessica had posted another photo of her ski outfit -- boots and all -- with the caption: “Skiing with the kiddos today. This is far as I got…."

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The new family of five celebrated its first Christmas with 9-month-old baby girl Birdie Mae plus 6-year-old Ace Knute and 7-year-old Maxwell “Maxi” Drew. Ashlee spent the day with her kids: 4-year-old daughter Jagger and 11-year-old son Bronx.

The older cousins' bonds are very strong, according to Evan. He previously told Page Six, “[Jessica's] kids already, Ace and Max, all are best friends with Jagger and Bronx, so yeah, it’s amazing."

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“They love each other and Ace and Maxwell are almost like big brother and sister,” he added.