Marriage in question is Dec quarter 1899 Elizabeth Trist St George Hanover Square volume 1a page 1020 with options for spouse Frederick George Pike or Rowland White.
Mother's maiden names are shown in the
birth index from Sep Qtr 1911 onwards.
You can use the index to search for any PIKE children born to a mother with the maiden name TRIST, and then for any WHITE children in the same way. It's not a foolproof method because one or both couples may have had no children after 1911, but it may give you an indication.
In order to be 100% sure, you will need to purchase the 1899 marriage certificate. The marriage information is not online, and won't be at least until FindMyPast have finished digitising the Westminster parish registers. Even then it may not be online, if the marriage was a civil one or in a nonconformist chapel.