I see no evidence for Elizabeth Allen, 1674-1722, having married a Francis Browne, nor having children.
Her children by William Gerard Tucker (1671-1733) span her childbearing years after marriage in 1693/94. through 1707.
As for Francis Browne being 4th Viscount Montagu (http://thepeerage.com/p42767.htm#i427666), this is neither likely nor probable. He never left England, her married Lady Mary Herbert, and died with any children.
Francis Browne, 4th Viscount Montagu, died in 1708, so there was no time period in Elizabeth Allen's life where she could have married him ... assuming he ever left England and was available for marriage.
