Being WordPress, I assume RewriteEngine is already on.
Important! Errors in htaccess files can crash your site, keep a working backup file
In its simplest, there will be a rewrite condition and a rewrite rule (when this, do this)
https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html#page-header
Under RewriteCond Directive there is
Syntax: RewriteCond TestString CondPattern [flags]
There are many "TestString"s but I think REQUEST_URI would work here.
The “CondPattern” could simply be the uppercase name.
In this use case you want to not use the optional [NC] (no case) flag. It would create an endless loop and cause a server error.
Thus far
RewriteCond {REQUEST_URI} JENNANDLUCAS
Under RewriteRule Directive there is
Syntax: RewriteRule Pattern Substitution [flags]
“Pattern” can be very complex regex, but in this case I think it can be relatively simple
“Substitution” will be what you want to use, i.e. the lowercase
“Flag” could be [R=301]
(redirect moved permanently)
So this should work
RewriteCond {REQUEST_URI} JENNANDLUCAS
RewriteRule ^/JENNANDLUCAS(.)* /jennandlucas$1 [R=301]
Untested and I might be missing something, but you can give it a try. Just be prepared to revert to your backup file if you need to.