Well in the 1899 city directory (compiled 1898) we have the last listing of Brown&Connor in Chicago, then we have the March 1903 newspaper announcement of the new business Caldwell&Anderson opening at 2 Oliver Row, South Bend.
Which could mean they married between 1898 and 1903 but probably at the beginning of this period since they divorced in 1904.
Ivy stated her birth date as 1891 and arrival in the US as 1893. Ivy was 27 in the 1920 census (birth 1893ish), 39 in the 1930 census (birth 1890ish and stated age at marriage of 24 - that was in 1914, making birth 1890ish). 1940 census she was 46 (so birth 1894ish).
It's still looking like Ivy was born before they married, and she was likely to be Jeanette/Janet's daughter rather than stepdaughter as she had the same middle name of Isobel (or just a popular name and a coincidence?). So we're looking for an Ivy Isobel Brown birth 1890-95 and possibly in Lakeside, Chicago, where Brown&Connor were first listed in the 1897 city directory, compiled 1896?