In RewriteRule it wouldn't match http or https in it, you may try following.
please make sure you clear your browser cache before testing your URLs.
RewriteEngine ON
RewriteCond %{HTTP_HOST} ^(?:www.)olddomain.com [NC]
RewriteCond %{REQUEST_URI} ^/parentage/oldtitle/?$ [NC]
RewriteRule ^(.*)$ https://www.newdomain.com/newtitle [R=301,L]
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