The internal names are a complete disaster. You should, technically, be seeing separate family names as show below in bold text. But because the internal names are such a mess, font managers and apps are doing their best to try and make sense of how they should be grouped.
Under High Sierra, Quark XPress, the Adobe apps, Office 365 and others I tried simply listed all fonts under one family name each of Merriweather, Montserrat and Montserrat Alternates. But below is the jumble of actual internal names:
Merriweather family
Regular - style name is Regular. Full, Menu and FOND names do not match.
Bold - style name is Bold. Full, Menu and FOND names do not match.
Bold Italic - style name is Bold Italic. Full, Menu and FOND names do not match.
Italic - style name is Italic. Full, Menu and FOND names do not match.
Merriweather Light family
Light - style name is Regular
Light Italic - style name is Italic. Full, Menu and FOND names do not match.
Merriweather Black family
Black - style name is Regular
Black Italic - style name is Italic
Monserrat family
Bold - style name is bold
Bold Italic - style name is bold italic
Italic - style name is Italic
Regular - style name is Regular. Full, Menu and FOND names do not match.
Montserrat Black family
Black Italic - style name is Italic
Black - style name is Regular. Full, Menu and FOND names do not match.
Montserrat Medium family
Medium - style name is Regular
Medium Italic - style name is Italic
Montserrat ExtraBold family
ExtraBold - style name is Regular
ExtraBold Italic - style name is Italic
Montserrat ExtraLight family
ExtraLight - style name is Regular
ExtraLight Italic - style name is Italic
Montserrat Light family
Light - style name is Regular
Light Italic - style name is Italic
Montserrat SemiBold family
SemiBold - style name is Regular
SemiBold Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Thin family
Thin - style name is Regular
Thin Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternatives family
Bold - style name is bold. Full, Menu and FOND names do not match.
Bold Italic - style name is Bold Italic. Full, Menu and FOND names do not match.
Italic - style name is Italic. Full, Menu and FOND names do not match.
Regular - style name is Regular. Full, Menu and FOND names do not match.
Montserrat Alternates Light family
Light - style name is Regular
Light Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternates Medium family
Medium - style name is Regular
Medium Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternatives Black family
Black - style name is Regular
Black Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternates SemiBold family
SemiBold - style name is Regular
SemiBold Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternatives ExtraBold family
ExtraBold - style name is Regular
ExtraBold Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternatives ExLight family
ExtraLight - style name is Regular. Full, Menu and FOND names do not match.
ExtraLight Italic - style name is Italic. Full, Menu and FOND names do not match.
Montserrat Alternates Thin family
Thin - style name is Regular
Thin Italic - style name is Italic. Full, Menu and FOND names do not match.
