Hi Malay ,
Which delete button you are mentioning here ?
Is it the default delete button of mendix ?
Can you please elaborate your question or where you are facing this issue.
Also if it is a data grid you can look into something below as it might be a problem with Selection mode of the grid
Currently on you are enabling the button based on single check try out a OCH microflow where firstly you retrieve the selected objects using a boolean attribute in the XPath of retrieve database and then aggregate the list and if the count is >2 then you need to active the another attribute where that delete button activates based on second attribute.